The present invention relates to data communications and, in particular, to circuit arrangements that may be used in data communication transceivers, such as transceivers that may be used in carrier sense multiple access (“CSMA”) networks.
In CSMA networks, where a plurality of data communication transmitter/receiver devices (“transceivers”) share a communication medium or channel, it is often necessary to detect collision events. A collision occurs when there is simultaneous transmission of signals by two or more devices. In a well-controlled medium with baseband signaling, such as Ethernet, a collision can be detected simply by monitoring whether the average voltage level is out of a normal range. In media that are not well-controlled, such as residential telephone lines and transmission systems employing QAM modulation, such a method is ineffective because the average signal level is always near zero, with or without collision, and the relative signal levels between colliding transceivers can differ significantly, making collision detection difficult.